Several integrated electronic devices exist, in which two or more circuits are built on a single chip and supplied by a single, i.e. common power supply. In some cases, ripple (or other input noise) caused by one of the circuits may have a negative impact on the operation of another circuit. This problem occurs e.g. when an NFC contactless frontend is implemented on the same chip as a contact-card frontend and both frontends are to be supplied by a single battery. More specifically, a contact-card frontend usually includes a capacitive boost DC-DC converter (e.g. a voltage doubler) for regulating the supply voltage according to the requirements of the contact-card frontend. As the switching frequency of such a capacitive boost DC-DC converter is directly proportional to the load current, the switching may generate ripple within a frequency that is problematic for the contactless front end and may even cause the latter to malfunction. Other examples may involve an audio processing circuit which may be negatively influenced by input noise or ripple caused by a DC-DC converter supply varying load within the audible frequency range.
Attempts towards solving the above problems have been made, including reducing ripple by adding additional resistances in the input of the DC-DC voltage doubler with feedback loop. However, such techniques require a huge area for additional series switches, and moreover, they require sensing of the load current. This also introduces control loop delay in the system. In such a scenario, during this delay if the RF frontend is ON, then there are chances of high magnitude ripple disturbing the RF frontend operation.
There may thus be a need for a simple and efficient way of overcoming the above drawbacks.